Telephone-exchange system



A. H. DYSON.

TELEPHONE EXCHANGE SYSTEM.

APPLiCATlON FILED JUNE 1. 9:5.

1 307,489. Patented June 24, 1919.

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TELEPHONE EXCHANGE SYSTEM.

I APPLICATION HLED JUNE 7, 1915 4 SHEETS-SHEET 3.

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A. H. DYSON.

TELEPHONE EXCHANGE SYSTEM APPLICATION EILED JUNE 7. 1915.

1 ,307,4- 89. Q Patented June 24, 1919.

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UNITED STATES OFFICE.

ALFRED n. DYSON, or MONTCLAIR, NEW messy, nssie von; BY Mns vn nssiemvinnrs, T0 wnsrmm ELECTRIC COMPANY, moonronn'rnn, A oonronA' IoN or NEW roux.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented June 24, 1919.

To all whom it may concern:

Be it known that I, ALFRED H. DYSON, a. citizen of the United States, residing at Montclair, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone-En change Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and particularly to means associated therewith for preventing the ringing of busy lines to which a call has been extended. It is especially applicable to con- .nectors of automatic and semi-automatic telephone exchange systems.

It is desirable for traflic reasons in a telephone exchange system to permit certain operators, such as the operators at a toll or long distance switchboard or incoming operators, to establish connections with wanted lines regardless whether they are at the moment busy or idle. Thus in an automatic or semi-auton'iatic exchange it'becomes neces sary, in order to meet the traffic requirements referred to, to force connections to busy lines in some manner regardless of the test ing means at the connectors which ordinarily operate to reject connections to busy lines.

In such systems, upon the seizure of the desired line, ringing current is automatically appliedto this line, andif the desired line is busy when the connection was established,

the called subscriber will hear the noise of I the appliedringing current in his receiver. It is the object of this invention to provide means whereby. if a connection is extended to a busy line, the application of the ringing current is automatically prevented. a

The invention will be more fully understood by reference to the accompanying drawings illustrative of the circuits of a semi-automatic system. Figures 1, 2 and 3 are to be placed adjacent one another from left to lllgili) in numerical order, and Fig. 4 below Fig, 1. Fig. 1 represents a toll line and connecting apparatus of a toll operators switchboard; and the circuits of a cordless incoiningi selector; Fig. 2, part of the cirseas of a line selector or connector; Fig. 3,

diagrammatically, certain portions of the connector structure, part the circuit connections thereof and the circuits of the local subscribefis line; and Fig. 4, certain of the circuits of a sender apparatus which is similar to the sender apparatus disclosed in patent to A, E. Lundell, No. 1,168,319, dated January 18, 1916, adapted for manipulation by an operator when associated with the cordless incoming selector of Fig. 2.

The structure and arrangement of the sender has no bearing on the present invention, and instead of the sender described in the above mentioned patent, any other -revertive impulse sender, that is to say, a sender which is adjusted to receive a certain number of impulses in response to the operation of selectively operableswitching devices, may be used without departing from the spirit of the invention, which is directed to the signaling of telephone stations. Obviously, instead of a revertive impulse sender, an impulse sender may be used by means of which the selector switches are directively set.

Only a general outline of the sender arrangement shown in the mentioned patent is given in the drawings, and the operating positions ofthe sequence switches shown in Figs. 1 and 4 are diflerent fromthose used in the cited patent. shown in Fig. 2 of the patent, is represented at 401; only two wipers 108 and 409 and two terminals adapted to be engaged by \the wipers being shown. These wipers correspond to the third and fifth wipers of the cord finder shown the mentioned patent.

In order to simplify the circuits shown in Figs. 1, 2 and 3 of the patent, a single circuit is shown extending between the sender and the controlling apparatus of the selector 104 where a plurality of circuits are shown in the patent. Only one sequence switch 400 is shownin Fig. 4; for performing functions which are usually performed by twoseqnence switches. This sequence switch. therefore is a combination of the sequence switches 300 and 400 shown in the patent. Under the control of a circuit including conduet r .403 and a sequenceswitch contact 119, the

The cord finder X;

quence switch 400 may be moved out of position 1. Sequence switch contact 119 is a combination of sequence switch contacts 206 and 208 of the patent, conductor 403 corresponds to conductor 305, and sequence switch spring 404 to sequence switch spring 304 of the patent. Relay 405 corresponds to relay 309 of the patent. In order to simplify the circuits, this relay is shown as controlling the movement of sequence switch 400 out of position 1, although relay 309 does not perform this function. Instead of the energizing circuit including the right-hand winding of relay 309 of the patent, and the holding circuit including the left-hand armature and winding of relay 309, a single circuit is shown including the right-hand top contact of sequence switch spring 404, conductor 410 and sequence switch spring 120. Conductor 410 corresponds to conductor 317, and sequence switch spring 120 to spring 209 of the patent. Relay 418 corresponds to relay 403, and relay 417 to relay 402. Conductor 412 corresponds to conductor 244, sequence switch spring 130 to spring 215, and relay 128 to relay 212 of the patent. The conduetor 235 and sequence switch contact 234 of the patent which are used when sending impulses beyond the selector shown in Fig. 1

of the patent are left out, conductor 412 and sequence switch spring 130 being used for this purpose. Conductor 411, by means of which sequence switch 100 may be moved into the talking position, corresponds to conductor 245 of the patent, and sequence switch spring 426 to sequence switch spring 429 of the patent.

For the purpose of producing various circuit changes required at the incoming selector (Fig. 1), there is provided a sequence switch 100, the circuits of the line selector (Fig. 2) also are controlled by a sequence switch 200, and the circuits of the sender (Fig. 4) are provided with a sequence switch 400. In the complete apparatus certain other sequence switch positions than those indicated adjacent to the contact springs may be used. For example, positions 2 to 12 inclusive of the sequence switch 100 may be utilized for the control or the circuits during the selecting operations of the incoming and line selectors preceding the final or units operation of the latter, which occurs in position 13 of the sequence switch 100, position 0 of sequence switch 200, and position 13 of sequence switch 400. As the pre liminary selecting operations, however, do

not have any special bearing on the invention clanned herein, and for the sake of brevity, a deserlptlon of the operations which take place in them and the detail circuits .in-

"volved therein are omitted.

The-heavy black lines runningthrough Flgsi 1 to-3 lnchrsive indicate the conductors through which a telephonic circuit may be established from station A 01 a toll line to station 13 of a local subscribers line. This connection in part includes means, such an answering plug and jack of an automatic switch, by which the call from station A is extended to a connecting circuit 101 of a toll operators position, and a calling plug 102 and trunk jack 103, by which the call is extended to the circuits of a cordless incoming selector 104 (Fig. 1). The latter connection may be established in accordance with in structions given by an incoming operator to the toll operator over an order wire, as to the particular incoming trunk or selector which the former operator assigns for the connection. By means of such an order wire (commonly used and not shown in the drawings), the toll operator had previously announced to the incoming operator the number of the wanted subscribers line. When the incoming operator has assigned the trunk, she depresses an assignment key 105 which starts into operation apparatus for temporarily associating a sender apparatus (Fig. 4) to the assigned trunk. The con nection between the trunk and the sender may be made through the usual cord finder 401, certain of the contacts of which are shown. The connection having proceeded, as stated, to the cordless incoming selector- 104, and the sender of Fig. 4 having been connected to the incoming trunk, the incoming trunk operator proceeds to effect the operation of the selector switches in the usual way. The operator may, for example, register the number on a series of keys of any known form of sender or controller. Such a keyboard and the detail circuits thereof not being material to the invention are not shown in the drawing, but there is shown for convenience in tracing the sequence of operations the immediate circuit connections of a well known counting relay sender effecting the operation of the selector switches. Under the control of such a sender the operator may first cause the incoming selector 104 to extend the call to a trunk leading to the circuits of a line selector 301 having access to a group of lines including the particular line wanted. The operation is effected automatirailly until the linal selector brushes are adjusted to the terminals of this line.

In a manner to be described more in detail later. the test relay 201 (Fig. 2) of the line selector 301 is ordinarily rendered effective immediately after the adjustment of the line selector 301 to test the condition of the selected line. But if it should be desired thatthe connection shall be established to this line regardless of whether or not it 1s busy, there is brought into operation a re test relay 202' Fig. 2) w'hich prevents .v

the test relay 201 from performing its function, and which also operates to apply the busy condition to the selected line, this latter function of the relay 202 being effected independently of the means for applying the test condition ordinarily provided by and in the operation of the test relay 201. In a no test operation, relay 202,- as will appear more in detail later, is energized a moment after the selector brushes are adjusted, a circuit path being provided for this purpose over the incoming trunk line from the sender (Fig. -.l-). If it had been desired by the toll operator that the connection be made regardless of the line condition, she

would have instructed the incoming operator to that effect, and the latter operator, preferably before operating the sender, would have depressedthe no test key 102. Normally, ringing current is automatically applied to the called subscribers line. If, however, the called subscriber is busy and the incoming operator has depressed the no test key 4-02, the called subscribe'fls line will not be rung and the subscriber, therefore, will not hear the noise caused by the ring ing current.

More in detail, the operation of the system is as follows:

Subscriber A desiring to initiate a toll call removes his receiver from the switchhook and causes thereby, in the well-known manner, the automatic or manual extension of his line to an operators cord circuit 101. The operator having learned by means of her telephone set (not shown) the number of the desired subscriber, transmits this number to an incoming or recording operator over an order wire (not shown) and extends the calling line 101 by inserting plug 102 into jack 103 to a trunk line 106, 107 in accordance with instructions received from the incoming operator. A circuit is closed now from ground through resistance 108, sleeve contacts of jack 103 and plug 102, and the coil of relay 100 to grounded battery, and the potential on the multiples of the sleeve of jack 103 is reduced to guard trunk line 100, 107 against other incoming calls. A further circuit: is closed from one side of battery 110 through the upper winding of relay 111, upper contact of relay 112, prin'iary winding of induction coil 113, trunk line 100, tip side of jack 103 and plug 102, cord circuit 101 including the winding of su aervisor 1 rel-a Y 11 1 and back throu h the ring side of plug 102 and ack 103, trunk line 107, primary of induction 0011 113,

' lower contact of relay 112 and lower windmg of relay 111 to the other poleof battery 110. Relays 114 and 111 become energized, the former causing the lighting of supervisory lampllz"), and the latter the energi i. relay 116,,

The incoming operator proceeds now to cause the building up of a connection between the calling subscriber A and the called subscriber B. First she depresses her assignment key 105 closing a circuit from ground through key 105, sequence switch spring 117, (in position 1), and power magnet of sequence switch 100 to grounded battery. Sequence switch 100 leaves its lirst position and moves under the control of the normal spring 118 into position 13. In position 2 of sequence switch 100 a circuit is closed from ground through sequence switch spring 119, conductor 4:03, spring 101 of sequence switch 400 (in position 1), and winding of relay 105 to grounded battery. Relay 105 upon energization closes a circuit through its armature and front contact and sequence switch spring 106 for the power magnet of sequence switch 100, and this sequence switch is under the control. of its normal spring 107 moved into position 13. After sequence switch 4:00 leaves its first position relay 105 is maintained energized through the right-hand top contact of sequence switch spring 4:04;, conductor 110 and sequence switcl spring 120 to ground. )Vhile sequence switch 100 is moving from position 1 to 13, circuits are established causing cord finder 4-01 to hunt with its wipers 108 and 409 for conductors 411 and 4112 assigned by the incoming operator, and after the cord finder brushes have been set, the incoming operator sends out the first set of numerical impulses designating the called line and causes, in the well-known manner, switch 104 to engage with its wipers 121, 122' and 123 the contacts in which terminate trunk 124, 125 and 126 leading to the final selector or connector 301. The setting of the selector switch 101- is acconuplished before sequence switch 100 reaches position 13.

In position 12 of sequence switch 100 and position 13 of sequence switch 100, a circuit is closed from grounded battery 127 through the coil of relay 128, sequence switch spring 129 (in position 12), sequence switch spring 130, conductor 412, cord finder brush 109, sequence switch spring 415 (in positions 1 to 18 and 13), resistance 110, windings of counting relay 117, and back contact and armature of relay 118, to ground. Relay 128 by attracting its right-hand armature prepares a locking circuit for itself, and

when sequence switch 100 reaches its 13th position this locking circuit is completed through sequence switch spring 129 (in positions 13 to 17). 1

When the wipers of selector switch 10 are set, a circuit is closed from ground through the left-hand armature and front contact of relay 128, right-hand bottom contact of sequence switch spring 131, wiper 121, conductor 124, sequence switch spring 203,

conductor 204- and winding of relay 205 to grounded battery 206. Relay 205 becomes energized and closes a circuit from ground through its left-hand armature and front contact, right-hand top and left-hand bot tom contacts of sequence switch spring 207 and winding of relay 208 to grounded battery 209; Relay 208 upon energization causes sequence switch 200 to leave its normal position and to move into position 6, by closing a circuit from ground through its left-hand armature and front contact, sequence switch spring 210, and the power magnet of sequence switch 200 to grounded battery. Relay 208 will not become decnergized when sequence switch 200 leaves its first position as this relay established a locking circuit for itself from grounded battery 209, through its winding, front contact and right-hand armature, resistance 211, test conductor 126, wiper 123, resistance 135 and sequence switch spring 136 to ground. Due to the closure of this circuit the potential on the terminal of conductor 126 is reduced to guard the trunk selected by switch 104 against other selector switches. Relay 205 remains also energized when sequence switch 200 leaves its first position, a circuit being closed from grounded battery 206, through the winding of relay 205, conductor 204, sequence switch spring 212 (positions 1 to 6), front contact and armature of relay 205, the top contact of sequence switch spring 203, conductor 124, wiper 121, the right-hand bottom con tact of sequence switch spring 131, and the front contact and armature of relay 128 to ground.

In position 6 of sequence switch 200, a circuit is closed forelevating-magnet 302 of connector 301 from grounded battery 303 through the winding of magnet 302, conductor 304, sequence switch spring 212, front contact and right-hand armature of relay 205, top contact of sequence switch spring 203, trunk conductor 124, wiper 121, the right-hand contact of sequence switch spring 131, and front contact and left-hand armature of relay 128 to ground. The elevating magnet 302 attracts its armature 305 and presses thereby brush rod 306 against a roller 307 which is constantly rotating in the direction indicated by an arrow. The line wipers 308 and 309, the test wiper 310, and the interrupter brushes carried by rod 306 are under the control of roller 307 caused to move in an upward direction. The wipers 308, 309 and 310 are adapted to engage the contacts of a terminal bank 314 in which subscribers lines terminate, and brushes 311,

312 and 313 are adapted to engage an interrupter plate 315. v v n Then brush 311 engages a conductingsegment and thereby in response to each' step taken by the brushre lay 417 is short cir 316, brush 311, conductor 317, brush 313,

conducting segment-318, conductor 319, sequence switch spring 216, (position to 6), conductor 217, and front contact and lefthand armature of relay 205 to ground.

After the impulse sending mechanism has returned to normal and thereby the wipers of connector 301 have been moved a number of steps as determined by the set position of the impulse sending mechanism, a circuit (not shown) is closed for relay 418. Relay 418 attracts its armature and causes sequence switch 400 to move out of position 13 into position 16, sequence switch spring 425 be ing closed in position 13 of the sequence switch. A circuit is now closed from ground through sequence switch spring 426, cord finder brush 408, conductor 411, sequence switch spring 117 and the power magnet of sequence switch 100 to grounded battery, and this sequence switch is moved into its fourteenth position. Sequence switch 100 is driven out of position 14 into position 16 by a circuit from ground through sequence switch spring 136 (bottom), conductor 137, armature and front contact of relay 116, sequence switch spring 138 and the magnet of the sequence switch to grounded battery. When sequence switch 100 leaves its position 13, the locking circuit of relay 128 is opened at sequence switch springs 129 and 130, and relay 128 in turn opens the energizing circuit of the elevating magnet of connector 301, the circuit of the latter being open also at sequence switch spring 131. The circuit of relay 405 is also opened at 120, this relay denergizes and drives sequence switch 400 into its normal position, the circuit being closed from ground through the armature and back contact of relay 405, spring 406 and magnet of sequence switch 400 to grounded battery. When sequence switch 400 leaves its position 16, which happens after-sequence switch 200 has moved out of position 7 the operators sending device and cord finder 401 are restored to normal.

Upon the deenergization of relay 128 and the opening of spring 131 in position 14 of sequence switch 100, relay 205 becomes deen'ergized' and "closes a circuit from ground through its left-hand armature and back contact, sequence switch spring 207 and the power magnet of sequence switch 200 to grounded battery. Sequence switch 200 is moved into position In this position relay 205 is again energized by a circuit closed from the plus pole of battery 206 through the winding of relay 205, conductor 201, sequence switch spring 203, (positions 1, 7 to 711;), conductor 12 1, wiper 121, the lefthand bottom contact or sequence switch spring 131 and the secondary winding of re peating coil 113 to the minus pole of battery 139. The energization of relay 205 causes sequence switch 200 to move into position 8, the circuit being closed through the lefthand armature and front contact of relay 205 and the right-hand contacts of sequence switch spring 207. 7

Due to the deenergization of magnet 302, the wipers 308-310 are arrested on the contacts in which the called subscribers line terminates. The brush rod 306 with wipers 308310 is maintined in its advanced position by a spring-pressed pawl 3241 adapted to engage openings in rod 306.

If the called substation line is idle, z. a. it full battery potential exists on test terminal 325, test relay 201 becomes energized, a circuit being established from grounded bat-- tery 326, through the winding of cut-oil relay 327, test conductor 328, terminal 325, wiper 310, conductor 329, sequence switch spring 220, low resistance winding of marginal test relay 201, the bottom contacts of sequence switch spring 221 and high resistance winding of relay 201 to ground.

Relay 201 closes a locking circuit for itself from ground through right-hand armature and back contact of relay 202, upper armature, front contact and low resistance winding of relay 201 and sequence switch spring 220 to grounded battery 326, the high resistance winding of relay 201 being short circuited upon the closure of this test circuit. The closure of this locking circuit reduces the potential on the multiples of test terminal 325 so as to prevent another test relay 201 from becoming energized and thereby rendering the line of subscriber B inaccessible to other incoming calls.

Relay 201 being energized, a circuit is closed from ground through the left-hand armature and back contact of relay 202, lower armature and front contact of relay 201, conductor 222, sequence switch spring 210 (positions 7 to 8, 141) and power magnet of sequence switch 200 to grounded battery. Sequence switch 200 moves out of position 8 into position 16. In position 15 of the sequence switch a ground is placed over sequence switch spring 223 on the winding of relay 202, and this relay becomes energized inparallel with the low resistance winding of test relay 201. Relay 202 by attracting its right-hand armature opens the locking circuit of relay 201 and closes a locking circuit for itself. During the conversation the called subscrib'ers line is guarded by the test circuit closed through the winding of relay 202.

When sequence switch 200 came into position 15, a circuit was closed from the plus pole battery through back contacts and arlnaturcs of relays 226 and 2 7, sequence switch spring 228, conductor 229, armature and back contact of relay 205, conductor 230, top contacts of sequence switch spring 231, winding of relay 232, back con tact of relay 233, conductor 121, wiper 121, sequence switch spring 131, and the secondary winding of repeating coil 113 to the minus pole ofbattery 139. Relay 232 becomes energized and closes a ringingcircuit for the called subscriber from ringing cur- .rent source 234-, through the winding of ringing relay 226, sequence switch spring 235, front contact and lower armature of relay 232 and the loop of subscriber B to ground,through the upper armature of relay 232. Relay 226 does not become energized until subscriber B removes his receivertrom the switchhook. I

In parallel with the circuit of relay 232, a circuit was closed from the plus pole of battery 236, through the lower winding of relay 227 and sequence switch spring 228, and through the circuit of relay 232 to the minus pole of battery 139; This relay, however, does not become energized, its lower winding being shunted by. a circuit from the plus pole offbattery 236, through the lower winding, armature and back contact of relay 227, and the armature and back contact of relay 226, to the plus pole of battery 225. I

Then the called subscriber B removeshis receiver from the switchhook, relay 226 becomes energized and opens the shunt around relay 227-, which also becomes energized. Upon the energization of relays 226 and 227 the circuit o1 relay 232 is opened, and this relay in turn, by retractingits armatures, opens the ringing circuit. k v

Upon the completion of the line circuit at the called subscribers station, supervisory relays 14:0 and 240 become energized. Belay 2 10 closesa circuit from. ground through its armature and front contact, and winding of relay 233 to grounded battery. Relay 233 upon energization closes a locking circuit for relay 227 ,which may be traced from ground through the armature and front contact of relay 233, fro11t.contact, armature and lower winding of relay 227 to grounded battery 236. Relay232 does not become energized upon the energization of relay 233, its winding being short-circuited from armature and :Front contact of relay 227 winding of relay 232, sequence switch spring 231, conductor 230, back contact and armature of relay 205, conductor 229,,sequence switch spring 228 and back to the armature of relay 227.

Upon the energization of supervisory relay 140, a circuit is closed from ground through the armature and front contact of relay 111, front contact and armature of relay 140 and winding of relay 112 to grounded battery 141. Upon the energization of relay 112, the circuit of relays 114 and 111 is opened, but relay 111 is maintained energized by a circuit from grounded battery 110, through the upper winding of relay 111, resistance 142, lower armature and front contact of relay 112 and lower winding of relay 111 to ground. Due to the deenergization of relay 114, supervisory lamp 115 is extinguished.

After the conversation is finished and the called subscriber hangs up his receiver, relays 240 and 140 become denergized. Due to the deenergization of relay 140, relay 112 becomes also deenergized and the winding of relay 111 is again included in its original energizing circuit, and relay 114 therefore causes again the lighting of lamp 115. The operator controlling the cord circuit 101 pulls plug 102 out of jack 103, causing thereby relays 114, 109 and 111 to release. Relay 111, upon deenergization, opens the circuit of relay 116, which by retracting its armature closes a circuit from ground through sequence switch spring 136, conductor 137, armature and back contact of relay 116 and winding of relay 150 which is slow to energize to grounded battery. Relay 150 closes then a circuit over sequence switch spring 138, and sequence switch 100 is moved over its 18th into its first position. In positions 17 and 18 of the sequence switch, selector 104 is restored in the well-known manner.

When the brush 123 of selector 104 disengages the terminal of conductor 126, relay 208 becomes deenergized and closes a circuit from ground over its left-hand armature and back contact, sequence switch spring 210 and power magnet of sequence switch 200 to grounded battery, and this sequence switch is moved into its 18th position. When sequence switch 200 leaves position 16, the circuit of no test relay 202 is opened at 223 and 220, and this relay becomes denergized. Relay 240 being deenergized, relay 233 opens the locking circuit of relay 227. Relay 227 becomes denergized when sequence switch 200 leaves its position 16. Further, a circuit is closed from grounded battery 303, through the winding of release magnet 330, conductor 331 and the right-hand contacts of sequence switch spring 216 to ground. Magnet 330 attracts its armature 332, causing thereby pawl 324 to disengage brush rod 306 and pressing the brush rod against roller 333 constantly rotating in a counter-clockwise direction. The roller 333 moves the brush rod in a downward direction, and when it reaches its normal position a circuit is closed from grounded battery through the power magnet of sequence switch 200, sequence switch spring 210, conductor 245, conducting segment 340 of interrupter e15, brush 312, conductor 317, brush 313, conducting segment 318, conductor 319 and sequence switch spring 216 to ground. Sequence switch 200 moves out of position 18 into position 1, and opens the energizing circuit of magnet 330.

The apparatus is now released to normal and ready for use in the buildingup of another connection.

If the called subscriber is busy, the potential on test terminal 325 is reduced so as to prevent the energization of test relay 201 in position 8 of sequence switch 200. A circuit is therefore closed from grounded battery 206 through the winding of relay 205, conductor 204, left-hand top contact of sequence switch spring 213, right-hand bottom contact of sequence switch spring 214, lower armature and back contact of relay 201, and back contact and armature of relay 202, to ground. Relay 205 becomes energized and closes a circuit from ground through its left-hand armature and front contact, right-hand contacts of sequence switch spring 207, and power magnet of sequence switch 200 to grounded battery. for moving sequence switch into position 14. Release magnet 330 is new energized, a circuit being closed from grounded battery 303 through the Winding of magnet 330, conductor 331, sequence switch spring 250, back contact and lower armature of relay 201, and back contact and left-hand armature of relay 202 to ground. Under the control of magnet 330, connector switch 301 is returned to its normal position. A circuit is now closed from grounded battery through the power magnet of sequence switch 200, lefthand bottom contact of sequence switch spring 210, conductor 245, conducting segnient 340 of interrupter 315, brush 312, conductor 317, brush 313, conducting segment 318, conductor 319, right-hand bottom contact of sequence switch spring 216, to ground. Sequence switch 200 moves into position 17 and a busy tone is applied to the calling subscribers line from 251 through the top contacts of sequence switch spring 221.

The apparatus employed in the building up of the connection is restored in the same manner as above described when consider-- ing the severing of a connection extended to an idle subscriber.

- In order to insure the seizure of the called line irrespective of the electrical conditions existing on the same, prior to the sending out of impulses, the incoming operator depresses the notest key 402 and causes thereby the energization of relay 430, the circuit being from grounded battery 431 through resistance 432, right-hand winding of relay 430. Relay 430 closes from grounded battery 433 through its left-hand winding, armature and front contact and sequence switch spring 434 to ground, a locking circuit for itself, said locking circuit being maintained closed by sequence switch spring 434 from position 1 to 16 of sequence switch 400.

The connection is built up in the same manner as before stated until sequence switch 200 reaches position 7, and sequence switch 100 position 13. A circuit is now closed from grounded battery 326 through the winding of cut-off relay 327, test conductor 328, terminal 325, wiper 310, conductor 329, sequence switch spring 220, winding of no test relay 202, sequence switch spring 223, armature and back con.- tact of relay 205, sequence switch springs 214 and 213, conductor 125, wiper 122, sequence switch springs 129 and 130, conduc tor 412, cord finder brush 409, sequence switch spring 415, and armature and front contact of relay 430, to ground. Relay 202, unlike relay 201 is adapted to be energized even if the potential on test terminal 425 is lowered. Thus due to the closure of the above circuit, relay 202 becomes energized in series with relay 327. By attracting its left-hand armature, relay 202 closes a ocking circuit for itself, and by attracting its right-hand armature it closes a circuit from ground through its front contact and right-hand armature, sequence switch spring 228 and upper winding of relay 227 to grounded battery 236. Due to the closure of this test circuit including relay 202, no relay 201 can become energized when a connector associated therewith is set on the terminals of this called subscribers line.

As in position of sequence switch 200 and in position 13 of sequence switch 100 relay 205 is energized, sequence switch 200 is moved through from position 7 into position 8 by a circuit from ground through the lefthand armature and front contact of relay 205, right-hand contacts of sequence switch 207 and the power magnet of sequence switch 200 to grounded battery. Sequence switch 200 is moved out of position 8 through position 14 into 16 by a circuit from grounded battery through the power magnet of sequence switch 200, sequence switch spring 210, conductor 222, to bottom contacts of sequence switch spring 231, conductor 245, and front contact and armature of relay 202 to ground.

Relay 227 being slow to release, will stay up while sequence switch 200 moves from position 7 to 16, the original energizing circuit of this relay being open at 228. In position 15 of sequence switch 200, relays 240 and 233 are energized and a locking circuit is closed for relay 227 in the above described manner. I

Due to the fact that relay 227 is energized as soon as the sequence switch reaches its position 7, no ringing current is applied to the called subscribers line, the winding of relay being short-circuited through the armature and front contact of relay 227.

The apparatus is released in the same manner as above described.

lVhat is claimed is:

1. In a telephone system, incoming and outgoing lines, a selector switch, means for operating said switch to seize an outgoing line whether busy or idle, a talking connection established and maintained thereupon between the calling incoming line and the seized outgoing line, automatic means for applying signaling current to a seized outgoing line, and means for preventing the operation of said automatic means if said connection is extended to a busy outgoing line.

2. In a telephone system, a plurality of lines, a line selector and means for testing selected lines, automatic means for signaling selected lines, a relay individual to said sclector adapted when actuated to render the testing means ineffective, means controllable at will for actuating said relay before the line can be tested and means controlled by said relay for preventing the operation of said automatic means.

3. In a telephone system, a plurality of lines, means comprising selector switches and a connector switch for connecting a calling line to a called line, a relay associated with said connector and adapted when actuated to connect signaling current to the seized called line, testing means for preventing the seizure of a busy called line, means operable at will for preventing the operation of said testing means, and means controlled by said last mentioned means for short-circuiting said relay.

4. In a telephone system, an outgoing line, a selector switch, means for causing said switch to connect with an outgoing line whether busy or idle, signaling means, a device having a plurality of positions, means actuated upon the operation of the selector switch for moving said device into a certain position, means operated in the certain position of said device when the seized outgoing line is idle for automatically connecting said signaling means to such line, and means operative in said certain position of the device when the seized line is busy for preventing the connection of said signaling means to the busy outgoing line.

5. Inv a telephone system, an incoming line, a selector switch having stationary and movable contacts, telephone lines terminating in szticlstavtionzu'y contacts, trunk 0011- (luotors terminating in saicl movable contacts, means for operating said selector to seize by means of its movable contacts a line terminating in a stationary contact, whether such line is busy or idle a talking connection established and maintained between said incoming line and the trunk line terininating in the operated movable Contact irrespective of the busy or idle condition of the seized outgoing line, and auto matic means operative only if the seized outgoing line is iclle for applying signaling current thereto.

In witness whereof, I hereunto subscribe my name this 1st (lay of June A. 1)., 1915.

ALFRED H. DYSON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C." 

